1. Field of the Invention
The present invention relates an improved structure of electrical signal connector and more particularly, to such an electrical signal connector, which facilitates alignment, insertion and installation of a mating cable. Subject to the characteristic that the barbed flange of the core tube is suspending in the cylindrical casing near the end edge of the tubular body, the invention facilitates mounting of a mating cable without causing damage to the aluminum foil shield of the mating cable.
2. Description of the Related Art
Following fast development of communication technology, signal transmission requires high stability and rapid speed. In consequence, different communication wire materials, from the early flat cable design to the modern round cable and optical cable designs, have been created to enhance signal transmission speed and capacity. Subject to the application of telephone technology, video technology and internet technology, global communication becomes faster and cheaper. Transmission of video signal through a cable assures signal stability and reliability. Therefore, closed-circuit TV is developed after the application of wireless TV and satellite TV. Establishing a closed-circuit television system requires installation of cables between the provider and the subscribers. When a cable is extended to a house, an electrical signal connector must be used to connect the cable to an indoor electric or electronic device. A conventional electrical signal connector A for this purpose, as shown in FIGS. 9˜11, comprises a casing A1 having a seam line A11, and a crimping tube A2, which is forced into the casing A1 by a tool to secure the inserted cable B to the casing A1. However, if the crimping tube A2 is not kept in alignment with the seam line A11 during installation, the crimping tube A2 may break. Further, when the cable B is stretched accidentally, the center conductor B1 of the cable B may be forced out of position, causing a poor contact and signal transmission instability. Further, the crimping tube A2 must be sleeved onto the cable B before insertion of the cable B into the casing A1. This installation procedure is inconvenient.
Taiwan utility number M255573, application series number 93200319, issued on Jan. 11, 2005, discloses an electrical signal connector C, as shown in FIG. 12. According to this design, the electrical signal connector C comprises a locknut C1 having a coupling flange C11, a sleeve C2 having a coupling groove C21 coupled to the coupling flange C11 of the locknut C11, a bushing C3 inserted into the axial hole C20 of the sleeve C2 and having a stepped flange C31, and a core tube C4 mounted in the bushing C3 and having a coupling portion C41 abutted against the stepped flange C31 of the bushing C3. The installation of this design of electrical signal connector requires the use of a hand tool. When connecting the electrical signal connector to a connector at an electronic device, the core tube C4 and the bushing C3 are forced into engagement with each other and movable in the axial hole C20 of the sleeve C2. According to this design, the locknut C1 of the electrical signal connector C has a big size and high manufacturing cost, and can only be rotated by hand without tool. Fastening the locknut C1 by hand cannot achieve high connection tightness. Further, the end edge C42 of the core tube C4 is spaced from the outer end C22 of the sleeve C2 at a distance. The user cannot see the position of the end edge C42 of the core tube C4 during installation of a cable, complicating the installation.
FIG. 13 illustrates another electrical signal connector according to the prior art. This design is substantially similar to the design shown in FIG. 12 with the exception that a spring member C5 is set between the coupling flange C11 of the locknut C1 and the outer wall C32 of the stepped flange C31 of the bushing C3 to impart a pressure to the bushing C3 and the core tube C4 in direction away from the locknut C1 so that the end edge C42 of the core tube C4 can be kept close to the outer end C22 of the sleeve C2 to facilitate alignment and installation of the cable B. However, this design of electrical signal connector still has the drawbacks of numerous component parts, complicated manufacturing process and complicated installation procedure.
In view of the drawbacks of conventional electrical signal connectors, U.S. Pat. No. 5,470,257 discloses an improved electrical signal connector, entitled “radial compression type coaxial cable end connector”. According to this design, as shown in FIG. 14, the radial compression type coaxial cable end connector has a connector body comprising a tubular inner post D2 extending from a front end to a rear end, and an outer collar D1 surrounding and fixed relative to the inner post D2 at a location disposed rearwardly of the front post end. The outer collar D1 cooperates in a radially spaced relationship with the inner post to define an annular chamber with a rear opening. A fastener D at the front end of the inner post D2 serves to attach the end connector to a system component. A tubular locking member E protrudes axially into the front open side D11 of the outer collar D1. The cable B is inserted from the outer end E1 of the tubular locking member E into the chamber E0 in the tubular locking member E and kept in alignment with the outer end D21 of the inner post D2, and then a hand tool is operated to move the tubular locking member E and the cable B into the chamber D10 in the outer collar D1,enabling the center conductor B1 and inner insulator B2 and aluminum foil shield B3 of the cable B to be engaged into the axial hole D20 of the inner post D2. In actual use, this design of radial compression type coaxial cable end connector still has drawbacks. For example, the outer end D21 of the inner post D2 is kept away from the outer end E1 of the tubular locking member E at a distance. During installation of the cable B, it is difficult to keep the center conductor B1 and inner insulator B2 and aluminum foil shield B3 of the cable B in alignment with the axial hole D20 of the inner post D2. After insertion of the cable B into the inner post D2, the center conductor B1 of the cable B may be deformed, and the aluminum foil shield B3 of the cable B may be damaged, causing signal transmission instability.
In order to eliminate the drawbacks of the aforesaid prior art designs, an improved coaxial cable connector is created. According to this design, as shown in FIG. 15, the coaxial cable connector comprises a locknut F, an outer tubular member F1 connected to the locknut F, an inner tubular member F2 mounted in the outer tubular member F1, a barrel G slidably coupled to the outer tubular member F1, and a guide tube F3 connected to the axial hole F20 of the inner tubular member F2. The guide tube F3 has an axial guide hole F30 defined therein and extending through front and rear ends thereof. The front end of the guide tube F3 extends to the front side G1 of the barrel G. Because the front end of the guide tube F3 is kept in flush with the front side G1 of the barrel G, the center conductor B1 of the cable B can be accurately inserted into the axial guide hole F30 of the guide tube F3, enabling the inner dielectric insulator B2 of the outer plastic sheath B to be stopped outside the guide tube F3. At this time, a hand tool is used to move the barrel G, the guide tube F3 and the cable B into the outer tubular member F1, enabling the guide tube F3 to pass out of the other end of the axial hole F20 of the inner tubular member F2, guiding the center conductor B1, inner dielectric insulator B2 and aluminum foil shield B3 of the outer plastic sheath B into the axial hole F20 of the inner tubular member F2. This design facilitates alignment of the cable during installation, however it still has drawbacks as follows:    1. This design of coaxial cable connector consists of a number of component parts, complicating installation. Further, the guide tube F3 must be thrown away after its service, not allowing for a repeated use. Waste of the guide tube relatively increases the connector cost.    2. The guide tube F3 must be made having a certain length so that the front end of the guide tube F3 can extend to the front side G1 of the barrel G. During insertion of the cable B, the long guide tube F3 tends to be vibrated, complicating alignment between the cable B and the axial hole F20 of the inner tubular member F2.
Therefore, it is desirable to provide an electrical signal connector, which facilitates quick and accurate connection of a coaxial cable without causing deformation of the center conductor of the coaxial cable or damage to the aluminum foil shield of the coaxial cable.